Separation of metals from ores



. will occur.

Patented Aug. 15, 1933 UNITED STATES PATENT OFFICE.

more, Md., assignors to The Davison Chemical Uompany, Baltimore, mm, a Uorporatmn or Maryland NoDrawing. -Application March 30, 1931 Serial No. 526,552

Claims.

This invention relates to processes of separating metals from ores and more particularly to the separation of metals such as copper, cobalt, and nickel from iron pyrites ore containing the same.

The object of the invention is to convert one or more of the above mentioned metals into their sulphates by introducing sulphur trioxide into a mass of such ore, or ash of such ore, while at a temperature suitable for the formation of one or more of such sulphates but unsuitable for the formation of iron sulphate. The sulphates formed by this process are water soluble and hence may be easily leached out with Water or water solutions.

It is recognized that prior inventors have introduced sulphur dioxide and air for the same purpose, but the results produced by the practice of such method are highly inferior to those produced by the process as discovered and practiced by the applicants. In the prior process, the amount of sulphur dioxide converted is only about 3 to 6 per cent, the conversion taking place after the sulphur dioxide has passed that portion of the ore, or ore ash, where the desired reactions The sulphur dioxide does not react to any appreciable extent with the cobalt or copper compounds, in such process, because these are still in the form of the sulphides. The small amount of conversion from sulphur dioxide to sulphur trioxide taking place in the ore burner produces, furthermore, such a weak sulphur trioxide concentration that its influence upon the ore roasting is in any case very small.

The instant process has the advantage in that the amount of sulphur trioxide present at any moment can be almost exactly controlled, whereas with sulphur dioxide and air, it cannot be. By the instant process a greater concentration of sulphur trioxide can be obtained, a more equal distribution and a greater flexibility achieved, since the amount of sulphur trioxide can be quickly changed Without interfering with the temperature or other conditions.

The temperature at which the instant process is effected is dependentupon the temperature of decomposition of the metal or metals which it is desired to separate. The proper temperature may be ascertained from the following table:

Decomposition Metallic temperature sulphate range FeSOl 492-560 0. 01180-1 (SSE-736 O. N lSOl 703-764" C. COSO-l 720770 C.

If it is desired to separate copper, nickel and cobalt compounds from the iron compounds, sulphur trioxide is introduced into the mass at a temperature above the decomposition of iron sulphate or 560 0., but below the decomposition temperature of the remaining sulphates, or 653 C.

The process of the invention has been found particularly advantageous when applied to the recovery of cobaltic material from ash resulting from the burning of iron pyrites ore containing cobalt in the production of sulphur dioxide for the manufacture of sulphuric acid.

In this manufacturing process, the pyrites ore or concentrates is burned in a furnace such as a shaft furnace. In practicing the present invention, sulphur trioxide may be introduced at the base of the furnace in contact with the hot ash or cinders before its removal, while at a temperature above the decompositon temperature of iron sulphate but below that of the cobalt sulphate. In this preferred embodiment, the temperature at the bottom of the furnace is maintained at about 40 C. At this temperature only a very small amount of the iron is broken down, but the cobalt, nickel, and copper are converted into the sulphates. The iron remains as the oxide and thus is insoluble in water, whereas the sulphated metals may be easily leached out.

Where iron pyrites is burned in a hearth furnace, the sulphur trioxide may be introduced at the bottom and either drawn off at the 'top, or at a point in the side above one to three or more hearths. Where the sulphur trioxide is withdrawn from the side of the furnace and before much contaminating gas becomes mixed therewith, such gas may be recirculated or reintrocluced into the bottom to keep a greater volume of rich gas in this part of the furnace.

It is obvious in the above mentioned process, as well as in such processes where other metals besides cobalt are present, such as copper and/or nickel, that the roasting may be eifected at the temperature at which the introduction of sulphur trioxide is to be effected or that the roasting may be practiced at other or higher temperatures and the ash brought as by cooling to the temperature at which it is desired to introduce the sulphur trioxide.

The sulphur trioxide may be either heated or cooled prior to its introduction in contact with the ore or ash.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In the process of separating cobalt from an ore containing a plurality of metal compounds, the steps comprising roasting the ore at a temperature below that at which the sulphate of cobalt decomposes but above that at which another metallic sulphate content decomposes, and while at that temperature introducing a gas consisting substantially exclusively of sulphur trioxide into the mass.

2. In the process of separating cobalt from a sulphid ore containing a plurality of metal compounds including cobalt compounds, the steps comprising roasting the ore and introducing a gas consisting substantially exclusively of sulphur trioxide into the mass at a temperature below the decomposition temperature of the sulphate of cobalt and above the decomposition temperature of another metallic sulphate content.

3. In the process of burning iron pyrites ore containing cobalt for use in the manufacture of sulphuric acid, the method of increasing the yield of cobalt sulphate comprising roasting the ore at a temperature below the decomposition temperature of cobalt sulphate but above the decomposition temperature of iron sulphate and introducing a gas consisting substantially exclusively of sulphur trioxide into the mass of ore prior to its removal from the furnace in which the roasting is effected.

4. In the process of separating metals from iron pyrites ore containing such, the steps comprising roasting said ore and while still hot from said roasting step and at a temperature maintained in the neighborhood of 540 C., introducing a gas consisting substantially exclusively of sulphur trioxide into the mass.

5. In the process of roasting pyrites ores containing valuable metals for the producing of sulphur dioxide gas in a furnace, the steps comprising introducing a gas consisting substantially exclusively of sulphur trioxide into the furnace near its cinder outlet into contact with the roasted ore, withdrawing unreacted sulphur trioxide from the side of the furnace before substantial contamination occurs, and reintroducing it into the furnace near said outlet in contact with the roasted ore.

ERNEST B. MILLER. GERALD C. CONNOLLY. 

